1. Field of the Invention
The invention relates to gas sampling assemblies and to air supply systems incorporating such assemblies and sterile packaging apparatus including such air supply systems.
2. Brief Review of the Prior Art
There are many circumstances where gas from a gas stream is flowed through a tube from a source to means utilizing the gas and where the gas may contain unwanted contamination in the form, for example, of microorganisms. An example of this is sterile packaging apparatus such as blow/fill/seal apparatus where the gas is air and is used to prevent contamination in the sterile packaging of product such as sterile liquids. Plainly, the presence in the air of contaminants such as micro-organisms can compromise the sterility of the packaging process and may result in packaged product being contaminated.
In order to remove contamination, the air supply is normally filtered through a filter (such as an HEPA filter (a high efficiency particulate-free air filter) or 0.2 xcexcm rated filter) having a rating sufficient to remove unwanted particulate contaminants such as micro-organisms. The filter can be inspected at the end of its life to see whether its integrity has been compromised to allow contaminants to enter the air stream supplied to the apparatus. This procedure may, however, render a large quantity of the articles unusable if it is found that the filter integrity has been compromised, since it is not possible to say when during the life of the filter the compromise occurred so making it necessary to remove all articles produced during the life of the filter.
In order to try and overcome this problem, it has been proposed to include a sampling assembly comprising a sampling port in the form of a pipe extending through a wall of the tube normal to the length of the tube. The assembly also includes a monitoring unit connected to the port and containing filter material which filters out contaminants in a sample airstream taken from the port. At intervals, the port is closed and the unit removed so that any contaminants on the filter material can be identified. In the case of biological materials, this may be done by removing the filter material from the unit, placing the material in a dish and then culturing any biological materials present. If culturing shows an unacceptable level of contaminants is present, the batch of articles produced with a contaminated airstream can be identified and removed.
It is a problem with a monitoring unit of this known type that the steps necessary to culture the biological materials can themselves introduce contamination on to the filter material. This can occur, for example, in transferring the filter material from the filter unit to the location at which culturing takes place. The culturing may therefore give a xe2x80x9cfalse positivexe2x80x9d by indicating the presence of contamination when, in fact, no contamination is present in the airstream, the indication arising from handling of the medium in the culturing steps. This can lead to articles being considered contaminated when this is not, in fact, the case.
According to another aspect of the present invention, there is provided a gas sampling assembly comprising a device for sampling a flow of gas and a sterile gas monitoring unit. An inlet tube may lead from the sampling device for passing sampled gas from the sampling device. The sterile gas monitoring unit may include a sterile inlet, a sterile material, and a port. The sterile inlet may be provided on the monitoring unit and may be connected to the inlet tube for supplying sampled gas to the monitoring unit. The sterile material may be within the monitoring unit for removing contaminants from the sampled gas. The port may be provided on the monitoring unit. The assembly may further comprise a first sterile closure and a second sterile closure. The first sterile closure may close the sterile inlet on completion of the passage of sampled gas to the monitoring unit. The second sterile closure may close the port and may be removable to allow the sterile supply to the sterile material of a material indicating the presence of particulates. The sterile gas monitoring unit may further include a transparent portion on the monitoring unit for viewing the indication produced by the indicating material.
In some embodiments, the invention may operate in accordance with a method of identifying the presence of particulate contaminants in a sample of gas from a gas stream comprising passing said gas sample through a monitoring unit, collecting particulate contaminants in said monitoring unit and then supplying to said monitoring unit a material for indicating the presence of said particular contaminant.
By culturing the material in situ, the chances of false positive results are minimized.